Anti-jamming and reduced interference global positioning system receiver methods and devices

ABSTRACT

Global navigation satellite system (GNSS) radio frequency signals broadcast from geo-stationary satellites 20,000 km above the earth when received by GNSS receivers are fundamentally weak. Accordingly, these GNSS receivers are vulnerable to accidental and deliberate interference from a range of synthetic sources as well as natural sources. Existing anti jamming technologies such as controlled reception pattern antennas, adaptive antennas, null-steering antennas, and beamforming antennas etc. are expensive and incompatible with many lower cost and footprint limited applications. However, in many applications the GNSS antenna is mounted upon a fixed or mobile element such that accidental and intentional jammers tend to be in the plane of the antenna or below it. Accordingly, there are presented designs and techniques to improve the anti-jamming or interference performance of GNSS receivers by further reducing the responsivity of the GNSS receiver to signals in-plane or below the plane of the antenna.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority as a continuationof U.S. patent application Ser. No. 16/369,711 filed Mar. 29, 2019;which itself claims the benefit of priority from U.S. Provisional PatentApplication 62/650,535 filed on Mar. 30, 2018, the entire contents ofeach being included herein by reference.

FIELD OF THE INVENTION

This patent application relates to patch antennas and more particularlyto methods and devices for improving the anti jamming performance ofpatch antennas and patch antennas for global positioning systems.

BACKGROUND OF THE INVENTION

A global satellite navigation system (satnav) or global navigationsatellite system (GNSS) is a system that exploits a network ofautonomous geo-spatially positioned satellites to provide geolocationand time information to a suitable receiver anywhere on or near theEarth where there is an unobstructed line of sight. Whilst timinginformation can be obtained from line of sight to a single satellitegeo-spatial location requires line of sight to three (at sea level) orfour satellites as a minimum. Whilst the original motivation for satnavsystems was for military purposes civil use of the systems was alsoallowed although until 2000 the United States Global Positioning System(GPS) that the military controlled signal degrading was removed althoughit may still be applied, and access may be selectively denied.

These factors led to a number of other systems being established withmore in development. Accordingly, as of December 2016 only the UnitedStates' Global Positioning System (GPS), Russia's Global'nayaNavigatsionnaya Sputnikovaya Sistema (GLONASS) and the European Union'sGalileo were globally operational GNSS. However, China is in the processof expanding its regional BeiDou Navigation Satellite System into theglobal BeiDou-2 GNSS by 2020 and India (NAVigation with IndianConstellation—NAVIC), France and Japan (Quasi-Zenith SatelliteSystem—QZSS) are in the process of developing regional navigation andaugmentation systems as well. Accordingly, today there are well over 200global navigation satellites in orbit for these GNSS. Table 1 belowlists the primary operating frequencies of these systems.

TABLE 1 Operating Frequencies of GNSS Systems (Nearest 1 MHz) SystemBeiDou Galileo GLONASS Owner China Europe Russia Freq. 1.561 GHz (B1)1.164-1.215 GHz (E5a/E5b) ~1.602 GHz (SP) 1.590 GHz 1.260-1.300 GHz (E6)~1.246 GHz (SP) 1.207 GHz (B2) 1.559-1.592 GHz (E2-L1-E11) 1.269 GHz(B3) Precision  10 m (Public)   1 m (Public) 4.5 m-7.4 m 0.1 m(Encrypted) 0.01 m (Encrypted) System GPS NAVIC Owner USA India Freq.1.57542 GHz (L1) 1.176 GHz (L5)  1.2276 GHz (L2) 2.492 GHz (S)  1.176GHz (L5) Precision 15 m  10 m (Public) 0.1 m (Encrypted)

By providing location and time information in all weather conditions,GNSS signals are now used in a variety of civil industries andapplications from construction and surveying, in-car and smartphonenavigation, oil, gas, agriculture etc. Already by 2010 the number of GPSreceivers had surpassed 1 billion and is probably closer to 2 billionwith consideration of GNSS receivers within consumer electronics such assmartphones, motor vehicles, activity, and fitness trackers etc.However, GNSS signals are transmitted from published radio frequenciesfrom geo-stationary satellites 20,000 km above the earth and transmit atlow powers by terrestrial microwave and RF system perspectives and thesesignals are weakened by the area of the earth's surface covered,atmospheric absorption, etc. such that the signals received arefundamentally weak. Accordingly, this low signal level makes GNSSreceivers vulnerable to accidental and deliberate interference from arange of synthetic sources, such as jammers, transmitters in adjacentbands, other radio-navigation satellite signals, etc. as well as naturalsources such as solar activity and geomagnetic storms.

Within the anti-jamming technologies are controlled reception patternantennas, adaptive antennas, null-steering antennas, and beamformingantennas which predominantly exploit phased array antennas to generatehighly directional antenna receiver responsivity pattern with azimuthalangle which are static or tunable (dynamic). However, such systems areexpensive and incompatible with many lower cost and footprint limitedapplications. In many applications the GNSS antenna is mounted upon afixed or mobile element such as a building, mast, vehicle, etc.Accordingly, accidental, and intentional jammers tend to be in the planeof the antenna or below it.

Accordingly, it would be beneficial to improve the anti jamming orinterference performance of GNSS receivers by further reducing theresponsivity of the GNSS receiver to signals in-plane or below the planeof the antenna.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

SUMMARY OF THE INVENTION

It is an object of the present invention to mitigate limitations withinthe prior art relating to patch antennas and more particularly tomethods and devices for improving the anti jamming performance of patchantennas and patch antennas for global positioning systems.

In accordance with an embodiment of the invention there is provided anantenna comprising:

-   a patch antenna comprising an upper electrode disposed atop a    dielectric body;-   a ground plane disposed below the dielectric body of the patch    antenna at a predetermined distance from the upper electrode;-   a plurality of conductive elements (directors), each director    disposed at a predetermined separation from the ground plane and    substantially parallel to the upper surface of the batch antenna.

In accordance with an embodiment of the invention there is provided anantenna comprising:

-   a patch antenna comprising an upper electrode disposed atop a    dielectric body operating at least at a first frequency band and a    second frequency band;-   a ground plane disposed below the dielectric body of the patch    antenna at a predetermined distance from the upper electrode;-   a plurality of first conductive elements (directors), each first    director disposed at a predetermined separation from the ground    plane and substantially parallel to the upper surface of the batch    antenna; and-   a plurality of second conductive elements (directors), each second    director comprising an opening within the central region of    predetermined dimension, disposed substantially around the plurality    of first directors at a predetermined separation from the ground    plane, and substantially parallel to the upper surface of the batch    antenna.

In accordance with an embodiment of the invention there is provided amethod of reducing the gain of a patch antenna at a predeterminedelevation by providing a parasitically coupled structure.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached Figures, wherein:

FIG. 1A depicts examples of global navigation satellite system (GNSS)receivers for precision timing applications;

FIG. 1B depicts examples of patch antennas for GNSS receivers;

FIG. 2A depicts a typical mechanical configuration for a patch antennafor a GNSS receiver;

FIG. 2B depicts the addition of a ground plane to a patch antenna for aGNSS receiver;

FIG. 2C depicts single feed and dual feed patch antennas for GNSSreceivers;

FIG. 2D depicts a dual feed patch antenna in combination with a 90°hybrid for extracting the right hand circular polarization signal;

FIG. 3 depicts the typical radiation pattern of a patch antenna withground plane;

FIG. 4 depicts a schematic of the addition of conductive planes(directors) above the active electrical plane of a patch antennaaccording to an embodiment of the invention;

FIG. 5A depicts schematically the adjustment in radiation pattern for aprior art patch antenna with ground plane relative to the inventivepatch antenna with ground plane and a plurality of conductive planes(directors) with the patch antenna disposed between the ground plane andlowermost conductive plane (director);

FIG. 5B depicts schematically the adjustment in radiation pattern forleft hand circular and right hand circular polarisations with aninventive patch antenna with ground plane and a plurality of conductiveplanes (directors) with the patch antenna disposed between the groundplane and lowermost conductive plane (director);

FIG. 6 depicts an external mechanical assembly for holding a pluralityof directors for an inventive antenna such as that depicted in FIG. 4prior to enclosure with a radome;

FIG. 7 depicts a single central mechanical assembly for holding aplurality of directors for an inventive antenna such as that depicted inFIG. 4 prior to enclosure with a radome;

FIG. 8 depicts an external mechanical assembly for holding a pluralityof directors for an inventive antenna such as that depicted in FIG. 4wherein the directors are held within the radome;

FIG. 9 depicts a single central mechanical assembly for holding aplurality of directors for an inventive antenna such as that depicted inFIG. 4 wherein the directors are held within the radome;

FIGS. 10 and 11 depict side elevation and perspective views of a patchantenna assembly comprising four mountings for the plurality ofdirectors attached to a frame upon which the ground plane and patchantenna are also mounted;

FIGS. 12A and 12B depict perspective cross-sectional views of theassembly depicted in FIGS. 10 and 11 with and without the radome;

FIG. 13 depicts a schematic of the addition of directors above theactive electrical plane of a patch antenna according to an embodiment ofthe invention for a dual frequency or dual band system;

FIG. 14 depicts a mechanical assembly for holding the two sets ofdirectors for an inventive antenna such as that depicted in FIG. 13prior to enclosure with a radome;

FIG. 15 depicts simulated gain pattern at 1580 MHz with different valuesof spacing between the directors for a multi-director design accordingto an embodiment of the invention in combination with a patch antenna;

FIG. 16 depicts simulated gain patterns for left-hand and right-handcircular polarizations at 1580 MHz for a GNSS receiver exploitingmultiple directors according to an embodiment of the invention comparedto the same patch antenna without the multiple director assembly; and

FIG. 17 depicts measured gain patterns along 60 azimuth cuts at 1580 MHzfor left-hand and right-hand circular polarizations at 1580 MHz for aGNSS receiver exploiting multiple directors according to an embodimentof the invention.

DETAILED DESCRIPTION

The present invention is directed to patch antennas and moreparticularly to methods and devices for improving the anti jammingperformance of patch antennas and patch antennas for global positioningsystems.

The ensuing description provides representative embodiment(s) only, andis not intended to limit the scope, applicability, or configuration ofthe disclosure. Rather, the ensuing description of the embodiment(s)will provide those skilled in the art with an enabling description forimplementing an embodiment or embodiments of the invention. It beingunderstood that various changes can be made in the function andarrangement of elements without departing from the spirit and scope asset forth in the appended claims. Accordingly, an embodiment is anexample or implementation of the inventions and not the soleimplementation. Various appearances of “one embodiment,” “an embodiment”or “some embodiments” do not necessarily all refer to the sameembodiments. Although various features of the invention may be describedin the context of a single embodiment, the features may also be providedseparately or in any suitable combination. Conversely, although theinvention may be described herein in the context of separate embodimentsfor clarity, the invention can also be implemented in a singleembodiment or any combination of embodiments.

Reference in the specification to “one embodiment,” “an embodiment,”“some embodiments” or “other embodiments” means that a particularfeature, structure, or characteristic described in connection with theembodiments is included in at least one embodiment, but not necessarilyall embodiments, of the inventions. The phraseology and terminologyemployed herein is not to be construed as limiting but is fordescriptive purpose only. It is to be understood that where the claimsor specification refer to “a” or “an” element, such reference is not tobe construed as there being only one of that element. It is to beunderstood that where the specification states that a component feature,structure, or characteristic “may,” “might,” “can” or “could” beincluded, that particular component, feature, structure, orcharacteristic is not required to be included.

Reference to terms such as “left,” “right,” “top,” “bottom,” “front” and“back” are intended for use in respect to the orientation of theparticular feature, structure, or element within the figures depictingembodiments of the invention. It would be evident that such directionalterminology with respect to the actual use of a device has no specificmeaning as the device can be employed in a multiplicity of orientationsby the user or users.

Reference to terms “including,” “comprising,” “consisting” andgrammatical variants thereof do not preclude the addition of one or morecomponents, features, steps, integers, or groups thereof and that theterms are not to be construed as specifying components, features, steps,or integers. Likewise, the phrase “consisting essentially of,” andgrammatical variants thereof, when used herein is not to be construed asexcluding additional components, steps, features integers or groupsthereof but rather that the additional features, integers, steps,components, or groups thereof do not materially alter the basic andnovel characteristics of the claimed composition, device, or method. Ifthe specification or claims refer to “an additional” element, that doesnot preclude there being more than one of the additional element.

As discussed above GNSS receivers are exploited within a wide range ofapplications within both the civil and military markets. Accordingly,these may range from small footprint low-cost consumer receivers forsmartphones, fitness trackers etc. through to high accuracy high gainreceivers specifically designed for timing and/or location. Referring toFIG. 1A there are depicted examples of antennas for timing applicationswithin high density cell/telecommunications tower applications whereinthe GNSS receiver is housed within a plastic transparent to wirelesssignals in the frequencies of interest as listed in Table 1 above. Sucha cover being commonly referred to as a radome. A radome being a dome orother structure protecting radar equipment and made from materialtransparent to radio waves. Accordingly, GNSS antennas such as thosedepicted within first to fourth images 110 to 140 respectively aredesigned to provide an industrial grade weather proof enclosure withoptions for mounting and including a microwave connector on the bottom.These will typically contain in addition to a wideband patch antennaelement a high gain (e.g., 40 dB or 50 dB) low noise amplifier (LNA) anda high rejection low loss out-of-band filter (e.g., a surface acousticwave (SAW) filter).

According to the requirements of the GNSS antenna a patch antenna suchas depicted by first to fifth patch antenna elements 150 to 190 may beemployed for the wideband patch antenna element. These being:

-   -   First patch antenna element 150 being a single band circular        patch antenna for GPS L1 and GLONASS G1 signals (Tallysman        Wireless TW2405);    -   Second patch antenna element 160 being a single band square        patch antenna for GPS L1 and GLONASS G1 signals (Tallysman        Wireless TW1320);    -   Third patch antenna element 170 being a dual band circular        antenna for GPS L1/L2, GLONAS G1/G2, Galileo D1 and BeiDuo B1        signals (Tallysman Wireless TW1829);    -   Fourth patch antenna element 180 being a dual band circular        antenna for GPS L1/L2, GLONAS G1/G2, Galileo E1 and BeiDuo B1/B2        signals (Tallysman Wireless TW3887); and    -   Fifth patch antenna element 190 being a triple band circular        antenna for GPS L1/L2/L5, GLONAS G1/G2/G3, Galileo E1/E5, BeiDuo        B1/B2 signals and L-band correction service coverage (Tallysman        Wireless TW3970).

Not depicted are reference antennas that provide broadband coverage suchas Tallysman Wireless VP6000 which provides coverage for all GNSSsignals plus L-band with a first window at 1164-1300 MHz and a secondwindow at 1525-1610 MHz. Alternatively, the VP6200 provides for anantenna for GPS L1/L2/L5, GLONASS G1/G2/g3, Galileo E1/E5a+b, BeiDouB1/B2+L-band correction (1164-1254 MHz+1525-1610 MHz) signals.

Referring to FIG. 2A there is depicted a typical circular patch antenna200A in plan and side elevation views wherein the circular patch antenna200A comprises a dielectric disc 210 with an upper surface metallization240, mounted directly upon a Printed Circuit Board (PCB) 220 withmounting holes 230 around the periphery and an electrical connection 250to a low noise amplifier contained with a metal shielding can visible inthe side elevation view, beneath the PCB 220. Optionally, the PCB 220may be provided without mounting holes 230 in order to reduce overalldimensions for example. With reference to FIG. 2A, Table 2 presentstypical dimensions for the first patch antenna element 150 in FIG. 1B.

TABLE 2 Dimensions for an Example of a Single Band Circular PatchAntenna Dimension Value d₁ (shielding can) 41 mm d₂ (patch element) 46mm d₃ (PCB Diameter 49.75 mm t₁ (patch thickness) 7.6 mm t₂ (patch +housing thickness) 4.0 mm

In most applications the patch antenna is employed in conjunction withan additional ground plane, in close proximity to the integrated PCB 220in order to enhance the antenna gain in the hemisphere above the groundplane, typically by 3 dB to 5 dB. As evident the sensitivity below theplane of the patch antenna is reduced by the use of a ground plane. Asdepicted in FIG. 2B the patch antenna 200B includes an additional groundplane 260 in close proximity (sometimes connected, but not necessarily)to which the antenna PCB 220, shown in FIG. 2A is attached. Accordingly,the electrical connection 250 in FIG. 2B is below the ground plane andis connected to an LNA contained in the shielding package shown belowthe additional ground plane 260, whilst the upper electrode 240 of thepatch antenna is above the ground plane.

Also depicted in FIG. 2A are feed connections 270 for the patch antennaas well as a central mounting hole to allow the patch antenna to bemounted in different configurations. As depicted in FIG. 2C a patchantenna may exploit a single feed or dual feeds as depicted in first andsecond imaged 200C and 200D, respectively. A single feed structureelicits an antenna response which is circular from the patch antenna asa of result critical coupling of the two axes through either the pinlocation and/or by strategically placed chamfers to the patch corners. Adual feed structure in which each feed is sited on a principle axis soas to constitute two linear, orthogonal antennas yields two feeds whichare may then be combined with a 90° hybrid 290 such as depicted in FIG.2D. Accordingly, the dual feeds, denoted as A Feed and B Feed, from adual feed patch antenna 200D are coupled to the 90° hybrid 290 whereinthey are combined resulting in the output signals for the right handcircular (RHC) polarization and left hand circular (LHC) polarisation onthe two outputs of the 90° hybrid 290. As GNSS signals are right handcircularly polarized then the RHC output is exploited in the subsequentelectronics whilst the LHC signal is coupled to ground via a loadimpedance, e.g., 50Ω load 280.

Accordingly, for embodiments of the invention described below anddepicted with respect to FIGS. 3 to 14 for GNSS patch antennas, be theysingle frequency, single band, multi-frequency, multiple bands, etc. thepair of linear orthogonal antennas with the dual feed structure imposesthe requirement that the patch antenna is circular, square, octagonal,dodecagonal etc. These and other geometries which may be employedexhibiting symmetry for a 90° rotation. Accordingly, other geometriesmay be employed including a PCB etc. and maintain the 90° rotationsymmetry.

However, it would evident that for other patch antennas without the dualfeed structure and pair of linear orthogonal antennas that othergeometries of patch antenna may be employed.

Referring to FIG. 4 there is depicted a schematic of an embodiment ofthe invention wherein a plurality of conductors, depicted a first tofourth conductive planes (directors) 410A to 410D, are disposed abovethe upper electrode of the patch antenna 400A. As depicted these firstto fourth conductive planes 410A to 410D are disposed at the followingdistances from the upper surface of the ground plane:

-   -   First conductive plane (director) 410A at l₁;    -   Second conductive plane (director) 410B at l₂=l₁+g₁;    -   Third conductive plane (director) 410C at l₃=l₁+g₂+g₁; and    -   Fourth conductive plane (director) 410D at l₄=l₁+g₃+g₂+g₁.

Accordingly, each of the first to fourth directors 410A to 410D acts asa parasitic element of the primary patch antenna 400A which is disposedbetween the fourth director 410D and the ground plane 260. Accordingly,with the appropriate gap(s); for example, g=g₃=g₂=g₁ or subsets of thegaps may be equal and other subsets at different gaps, then thedirectors as parasitic elements re-radiate their signals with slightlydifferent phases to that of the driven patch antenna. Accordingly,whilst these are not driven, the amplitude and phase of the inducedelectrical signals on the parasitic elements are dependent upon thedimensions of the parasitic elements and their spacing both betweenthemselves and to the driven element. Accordingly, the parasiticelements act to reinforce in the zenith direction of the antenna andreduce the gain in a direction at an angle relative to the plane of theantenna (i.e., the horizon for the antenna). Accordingly, as depicted inFIG. 5A the parasitic elements, for example first to fourth directors410A to 410D, in combination with the ground plane act to alter theradiation pattern from that depicted by first curve 510, to thatdepicted by second curve 520, whereby the gain at zenith (0°) isincreased and the gain at an elevation angle of Theta degrees above thehorizon (−90° and 90°) is substantially reduced.

Within the ensuing descriptions of embodiments and in respect of FIGS. 6to 17 the conductive planes are referred to as directors or parasiticelements are described. However, other embodiments may according to theperformance of the receiver required, footprint and volume requirements,etc. exploit other numbers of directors such as 1, 2, 3, 5, 6, etc. Theconductive planes (directors) are electrically conductive and hence maybe formed from a metal with low resistance and low density such asaluminum for example although other metals and alloys may be employedfor example provided that they achieve the desired cost and performancerequirements of the product. Accordingly, within embodiments of theinvention the directors may be also formed from copper, gold, silver,tungsten, steel, stainless steel etc. Optionally, the director may beformed from a thin film or thick film of a conductor upon a lowdielectric material such as FR4, teflon (glass weave), teflon(polytetrafluoroethylene, PTFE), polypropylene, and polyamide forexample.

Further, the conductive planes (directors) are described and depictedwith respect to their being surrounded by air. However, otherembodiments of the invention may exploit one or conductive planesembodied within insulating materials with high dielectric constants inorder to reduce the size of the conductors and their spacing. Suchmaterials may include ceramic, polyolefin, PTFE, polyetherimide (PEI),fused silica, sapphire, alumina, and beryllia for example.

Now referring to FIG. 6 there is depicted an external mechanicalassembly for holding a plurality of directors for an inventive antennasuch as that depicted in FIG. 4 prior to enclosure with a radome.Accordingly, as depicted the plurality of directors 410A to 410D aredisposed substantially parallel to the upper surface of the patchantenna 600A and held within first and second frames 610A and 610Brespectively which are atop first and second spacers 620A and 620B.First and second frames 610A and 610B may be the only pair of frames ormay be two of a number of frames around the periphery of the directorsholding them. For example, if the first and second frames 610A and 610Brespectively subtend a relatively significant portion of the periphery,e.g., 30°, 45°, 60° for example, then the directors are restrainedsufficiently in all directions. If the first and second frames 610A and610B respectively subtend a relatively small portion of the periphery,e.g., 10°, 15° for example, then additional frames may be required toretain the directors in position in all directions. For example, 3, 4,5, 6, etc.

As the current flowing within the directors will be circular within thedirector and highest at the periphery then the frames holding thedirectors should be non-conductive in order not to introduce losses viagrounding the directors to the frames. Accordingly, the frames may beformed from a variety of non-conductive materials although the samematerial as the radome may in many instances be the simplest designoption. Whilst single part designs for the first and second frames 610Aand 610B are depicted alternate arrangements may be considered withoutdeparting from the scope of the invention.

Referring to FIG. 7 there is depicted a single central mechanicalassembly for holding a plurality of directors for an inventive antennasuch as that depicted in FIG. 4 prior to enclosure with a radome.Accordingly, the central mounting 710 may be attached via a centralmounting hole within the patch antenna 700A via a screw, bolt etc.although other attachment means, assemblies may be considered. Forexample, the central mounting 710 may fit atop a frame with multiple“arms” that are attached to the ground plane or a frame within which orto which the ground plane and patch antenna 700A are attached. As thecurrent flowing within the directors is around the periphery the currentat their centers will be zero or near-zero such that a conductivematerial may be employed for the central mounting in addition to anon-conductive material. As depicted the central mounting 710 comprisesmultiple sections allowing each director to be mounted and then retainedas the next element of the central mounting is attached etc. However,alternate arrangements may be considered without departing from thescope of the invention.

Now referring to FIG. 8 there is depicted an external mechanicalassembly for holding a plurality of directors for an inventive antennasuch as that depicted in FIG. 6 wherein the directors are held withinthe radome rather than discrete frame(s) as described and depicted inFIG. 6 for example which are then enclosed within a radome. Accordingly,the “frame” and radome may be formed as a single piece part from anappropriate non-conductive material and the directors placed into theslots.

FIG. 9 there is depicted a single central mechanical assembly forholding a plurality of directors for an inventive antenna such as thatdepicted in FIG. 7 wherein the directors are held within the radomerather than discrete frame(s) as described and depicted in FIG. 6 forexample which are then enclosed within a radome.

FIGS. 10 and 11 depict side elevation and perspective views of a patchantenna assembly comprising four mountings for the plurality ofdirectors attached to a frame upon which the ground plane and patchantenna are also mounted. Accordingly, first to fourth directors 1030Ato 1030D are depicted retained in position by four frames 1010 which areattached to a base structure 1020. The patch antenna 1040 and its groundplane (not identified) are mounted within the base structure 1020 andthe microwave feed established through the bottom of the base structure1020 although within other embodiments the microwave feed may be throughthe side wall of the base structure, for example. This configuration isalso depicted in FIGS. 12A and 12B which respectively depict perspectivecross-sectional views of the assembly with and without the radome.

Within the preceding descriptions and discussion in respect of FIGS. 4and 6-12 a single set of conductive planes (directors) have beenconsidered for a patch antenna addressing a single frequency or singleband of operation, e.g., GPS L1+GLONASS L1, such as first and secondpatch antenna elements 150 and 160 in FIG. 1B. However, as noted abovedual band and triple band patch antennas may be employed such as thirdto fifth patch antenna elements 170 to 190 respectively in FIG. 1B.Accordingly, referring to FIG. 13 there is depicted a schematic of theaddition of directors above the active electrical plane of a patchantenna having similar radiation patterns and responses at multiplefrequencies according to an embodiment of the invention for a dualfrequency or dual band system. Accordingly, as depicted in first image1300A an outer ring conductive plane 1310 (director) is employed inconjunction with an inner conductive plane 1320 (director). Accordingly,as depicted in second image 1300B the spacings for the first to fourthinner directors 1320A to 1320D respectively is different to that for thefirst to fourth outer directors 1310A to 1310D respectively due to thedifference in frequency for the two GNSS signals. This concept could beextended as depicted in third image 1300C with outer ring directors1350, middle ring directors 1360 and inner directors 1370.

Referring to FIG. 14 there is depicted a mechanical assembly 1500 forholding the two sets of directors for an inventive antenna such as thatdepicted in FIG. 13 prior to enclosure with a radome. Accordingly, inorder to minimize the gap between the inner directors 1320A to 1320D andthe outer ring directors 1310A to 1310D then the outer ring directors1310A to 1310D exploit a non-conductive external frame mounting whilstthe inner directors 1320A to 1320D exploit a central mounting.Alternatively, a non-conductive mounting may be employed to mount aninner director 1320A to 1320D with respect to its respective outer ringdirector 1310A to 1310D at the appropriate spacing and then theseassemblies mounted with either an external frame or a central mounting.Such a connection being depicted in schematic 1550 wherein a connector1530 couples the inner director 1320 to the outer ring director 1310.Such a connector 1530 as discussed supra in respect of the frames mayaccording to the angle they subtend around the periphery of the innerdirector 1320 be only 2 such connectors or it may be 3, 4, 5, 6, etc.Optionally, it could be single ring connector.

As discussed supra the metallic directors and ground plane employed inconjunction with the patch antenna result in an improved performance inthe zenith direction and the establishment of a null in the lowerelevation of the RHC gain pattern for the antenna assembly therebyimproving the anti jamming and interference performance of the GNSSantenna. The nearest configuration to this being a Yagi-Uda antennaconfiguration. pattern.

Within the following description in respect of FIGS. 15 to 17 a designis presented which establishes a null close to the horizon where most ofthe terrestrial interfering signals are coming from and especially at anelevation of 15 degrees. It is light and very compact with a diameter of100 mm, a height of 101 mm and a weight of less than 370 g. This designwill be referred to subsequently as the anti jamming (AJ) GNSS (AJ-GNSS)antenna. As noted above the design methodology of a plurality ofdirectors allows for establishing of a null towards the horizon wherethe nulling is established in dependence upon the spacing between thedirectors FIG. 15 shows the variation of the nulling angle from 0 degreeto 25 degrees as the spacing between the directors is varied from 10 mmto 25 mm Also, it can be seen that maximum RHC gain at zenith variesfrom 7.9 dBic to 10 dBic.

The diameter of the directors will also have an impact on the gainpattern. Accordingly, the director diameter for the circular directorsemployed was set to optimize the response in the GNSS frequency band. Asnoted supra in respect of FIG. 5B adjusting the diameter and spacing ofthe directors to generate a very deep null in the gain pattern at thefrequency of interest

Now referring to FIG. 16 the simulated radiation gain patterns of anoptimized AJ-GNSS for 1580 MHz operation and a standard GNSS patchantenna are depicted for operation at 1580 MHz. The gain patterns atother azimuth and frequencies in the higher GNSS band for this optimizedAJ-GNSS similar. The AJ-GNSS exhibits a non-realized RHC gain at zenithfrom 8.7 dBic to 9.2 dBic which is close to 4 dB higher than thestandard GNSS patch. Additionally, the radiation gain null from theinventive design with the plurality of directors is evident within theRHC gain pattern at an elevation angle of 15 degrees. The RHC gain atthat elevation is more than 35 dB down relative to the maximum gainwhich represents an attenuation of approximately 25 dB compared to thestandard GNSS patch at that elevation angle. The LHC gain is increasedcompared to the standard GNSS patch but usually stays 30 dB below themaximum RHC gain at zenith and −19 dB below at horizon.

The AJ-GNSS simulated in FIG. 16 was measured using an anechoic chamberwherein the resulting experimental results are depicted in FIG. 17 . Themeasured gain pattern at 1580 MHz is in good agreement with thesimulation results. Axial ratio is a measure of an antenna's ability toreject the cross polarized portion of a composite signal with both RHCand LHC components. The worst case axial ratio values of the AJ-GNSSaccording to an embodiment of the invention are less than 0.9 dB at thezenith in the whole higher GNSS frequency band. This performanceprovides for the excellent multipath rejection capability of the AJ-GNSSaccording to an embodiment of the invention.

Specific details are given in the above description to provide athorough understanding of the embodiments. However, it is understoodthat the embodiments may be practiced without these specific details.For example, circuits may be shown in block diagrams in order not toobscure the embodiments in unnecessary detail. In other instances,well-known circuits, processes, algorithms, structures, and techniquesmay be shown without unnecessary detail in order to avoid obscuring theembodiments.

The foregoing disclosure of the exemplary embodiments of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many variations andmodifications of the embodiments described herein will be apparent toone of ordinary skill in the art in light of the above disclosure. Thescope of the invention is to be defined only by the claims appendedhereto, and by their equivalents.

Further, in describing representative embodiments of the presentinvention, the specification may have presented the method and/orprocess of the present invention as a particular sequence of steps.However, to the extent that the method or process does not rely on theparticular order of steps set forth herein, the method or process shouldnot be limited to the particular sequence of steps described. As one ofordinary skill in the art would appreciate, other sequences of steps maybe possible. Therefore, the particular order of the steps set forth inthe specification should not be construed as limitations on the claims.In addition, the claims directed to the method and/or process of thepresent invention should not be limited to the performance of theirsteps in the order written, and one skilled in the art can readilyappreciate that the sequences may be varied and still remain within thescope of the present invention.

What is claimed is:
 1. An antenna comprising: an upper electrodedisposed atop a dielectric body operating at a plurality of frequencies;a ground plane disposed below the dielectric body of the antenna at apredetermined distance from the upper electrode; and a plurality of setsof conductive elements where each set of conductive elements comprises aplurality of conductive planes where each conductive plane of theplurality of conductive planes in a set of conductive elements aredisposed at a predetermined constant spacing relative to one another anda conductive plane of the plurality of conductive planes nearest theground plane is disposed with the predetermined constant spacing fromthe ground plane; wherein an antenna gain of the antenna at a frequencyof the plurality of frequencies has a radiation gain null at apredetermined elevation determined in dependence upon the predeterminedconstant spacing of a predetermined set of conductive elements of theplurality of sets of conductive elements.
 2. The antenna according toclaim 1, wherein a first set of conductive elements of the plurality ofsets of conductive elements are circular; and each other set ofconductive elements of the plurality of sets of conductive elements is aseries of annular rings of defined inner radius and defined outerradius; and the plurality of sets of conductive elements do not overlapradially from a longitudinal axis along which the plurality of sets ofconductive elements are disposed.
 3. The antenna according to claim 1,further comprising a plurality of sets of electrically non-conductiveconnectors; wherein a first set of conductive elements of the pluralityof sets of conductive elements are circular; and each other set ofconductive elements of the plurality of sets of conductive elements is aseries of annular rings of defined inner radius and defined outerradius; and the plurality of sets of conductive elements do not overlapradially from a longitudinal axis along which the plurality of sets ofconductive elements are disposed; each set of electricallynon-conductive connectors of the plurality of sets of electricallynon-conductive connectors couples an inner conductive plane of theplurality of conductive planes in a set of conductive elements to anouter conductive plane of the plurality of conductive planes in anotherset of conductive elements; and the set of conductive elements of theplurality of sets of conductive elements having the outermost annularrings are mounted to a plurality of electrically non-conductive mountingelements disposed at predetermined positions around the periphery of theplurality of sets of conductive elements.
 4. The antenna according toclaim 1, further comprising a plurality of sets of electricallynon-conductive connectors; wherein a first set of conductive elements ofthe plurality of sets of conductive elements are circular; and eachother set of conductive elements of the plurality of sets of conductiveelements is a series of annular rings of defined inner radius anddefined outer radius; and the plurality of sets of conductive elementsdo not overlap radially from a longitudinal axis along which theplurality of sets of conductive elements are disposed; each set ofelectrically non-conductive connectors of the plurality of sets ofelectrically non-conductive connectors couples an inner conductive planeof the plurality of conductive planes in a set of conductive elements toan outer conductive plane of the plurality of conductive planes inanother set of conductive elements; and the first set of conductiveelements of the plurality of sets of conductive elements are mounted toa central electrically non-conductive mounting substantiallyperpendicular the upper electrode and passing through the centre of eachconductive element within the first set of conductive elements of theplurality of sets of conductive elements.
 5. The antenna according toclaim 1, further comprising a plurality of sets of electricallynon-conductive connectors; wherein a first set of conductive elements ofthe plurality of sets of conductive elements are circular; and eachother set of conductive elements of the plurality of sets of conductiveelements is a series of annular rings of defined inner radius anddefined outer radius; and the plurality of sets of conductive elementsdo not overlap radially from a longitudinal axis along which theplurality of sets of conductive elements are disposed; each set ofelectrically non-conductive connectors of the plurality of sets ofelectrically non-conductive connectors couples an inner conductive planeof the plurality of conductive planes in a set of conductive elements toan outer conductive plane of the plurality of conductive planes inanother set of conductive elements; the first set of conductive elementsof the plurality of sets of conductive elements are mounted to a centralelectrically non-conductive mounting substantially perpendicular theupper electrode and passing through the centre of each conductiveelement within the first set of conductive elements of the plurality ofsets of conductive elements; and the set of conductive elements of theplurality of sets of conductive elements having the outermost annularrings are mounted to a plurality of electrically non-conductive mountingelements disposed at predetermined positions around the periphery of theplurality of sets of conductive elements.
 6. An antenna comprising: anupper electrode disposed atop a dielectric body and a ground planedisposed at a predetermined distance from the upper electrode below theupper electrode; and a plurality of conductive elements disposed abovethe upper electrode where the plurality of conductive elements aredisposed at a constant spacing relative to one another and theconductive element of the plurality of conductive elements nearest theground plane is disposed with the constant spacing from the groundplane; wherein each conductive element of the plurality of conductiveelements is substantially parallel to the upper electrode; a gain of theantenna at a zenith is increased relative to the antenna gain at thezenith for the antenna alone; the gain of the antenna has a null at apredetermined elevation established in dependence upon the constantspacing of each conductive element relative to its neighbours within theplurality of conductive elements.
 7. The antenna according to claim 6,wherein the plurality of conductive elements are mounted to a centralmounting which is substantially perpendicular to the upper electrode andpassing through the centre of each conductive element.
 8. The antennaaccording to claim 6, wherein each conductive element of the pluralityof conductive elements has a predetermined geometry that exhibitssymmetry for a 90° rotation.
 9. The antenna according to claim 8,wherein the central mounting is at least one of electrically conductiveand electrically non-conductive.
 10. The antenna according to claim 6,wherein the plurality of conductive elements are mounted to a pluralityof mounting elements disposed at predetermined positions around theperiphery of the conductive elements.
 11. The antenna according to claim10, wherein the plurality of mounting elements are electricallynon-conductive.
 12. An antenna comprising: an upper electrode disposedatop a dielectric body operating at a plurality of frequencies; a groundplane disposed below the dielectric body at a predetermined distancefrom the upper electrode; and one or more sets of conductive elementswhere each set of conductive elements comprises a plurality ofconductive planes where each conductive plane of the plurality ofconductive planes in a set of conductive elements are disposed at apredetermined constant spacing relative to one another and a conductiveplane of the plurality of conductive planes nearest the ground plane isdisposed with the predetermined constant spacing from the ground plane;wherein an antenna gain of the antenna at a subset of the plurality offrequencies has a radiation gain null at a predetermined elevationdetermined in dependence upon the predetermined constant spacing of apredetermined set of conductive elements of the one or more sets ofconductive elements.
 13. The antenna according to claim 12, wherein afirst set of conductive elements of the one or more sets of conductiveelements are of a predetermined geometry; and any other set ofconductive elements of the one or more sets of conductive elements is aseries of annular implementations of the predetermined geometry; and theone or more sets of conductive elements do not overlap radially from alongitudinal axis along which the one or more sets of conductiveelements are disposed; and the predetermined geometry exhibits symmetryfor a 90° rotation.
 14. The antenna according to claim 12, furthercomprising a plurality of sets of electrically non-conductiveconnectors; wherein a first set of conductive elements of the one ormore sets of conductive elements are of a predetermined geometry; anyother set of conductive elements of the one or more sets of conductiveelements is a series of annular implementations of the predeterminedgeometry; the one or more sets of conductive elements do not overlapradially from a longitudinal axis along which the one or more sets ofconductive elements are disposed; the predetermined geometry exhibitssymmetry for a 90° rotation; each set of electrically non-conductiveconnectors of the plurality of sets of electrically non-conductiveconnectors couples an inner conductive plane of the plurality ofconductive planes in a set of conductive elements to an outer conductiveplane of the plurality of conductive planes in another set of conductiveelements; and the set of conductive elements of the one or more sets ofconductive elements having the outermost annular rings are mounted to aplurality of electrically non-conductive mounting elements disposed atpredetermined positions around the periphery of the one or more sets ofconductive elements.
 15. The antenna according to claim 12, furthercomprising a plurality of sets of electrically non-conductiveconnectors; wherein a first set of conductive elements of the one ormore sets of conductive elements are of a predetermined geometry; anyother set of conductive elements of the one or more sets of conductiveelements is a series of annular implementations of the predeterminedgeometry; the one or more sets of conductive elements do not overlapradially from a longitudinal axis along which the one or more sets ofconductive elements are disposed; the predetermined geometry exhibitssymmetry for a 90° rotation; the one or more sets of conductive elementsdo not overlap radially from a longitudinal axis along which the one ormore sets of conductive elements are disposed; each set of electricallynon-conductive connectors of the plurality of sets of electricallynon-conductive connectors couples an inner conductive plane of theplurality of conductive planes in a set of conductive elements to anouter conductive plane of the plurality of conductive planes in anotherset of conductive elements; and the first set of conductive elements ofthe one or more sets of conductive elements are mounted to a centralelectrically non-conductive mounting substantially perpendicular theupper electrode and passing through the centre of each conductiveelement within the first set of conductive elements of the one or moresets of conductive elements.
 16. The antenna according to claim 12,further comprising a plurality of sets of electrically non-conductiveconnectors; wherein a first set of conductive elements of the one ormore sets of conductive elements are of a predetermined geometry; anyother set of conductive elements of the one or more sets of conductiveelements is a series of annular implementations of the predeterminedgeometry; the one or more sets of conductive elements do not overlapradially from a longitudinal axis along which the one or more sets ofconductive elements are disposed; the predetermined geometry exhibitssymmetry for a 90° rotation; the one or more sets of conductive elementsdo not overlap radially from a longitudinal axis along which the one ormore sets of conductive elements are disposed; each set of electricallynon-conductive connectors of the plurality of sets of electricallynon-conductive connectors couples an inner conductive plane of theplurality of conductive planes in a set of conductive elements to anouter conductive plane of the plurality of conductive planes in anotherset of conductive elements; the first set of conductive elements of theone or more sets of conductive elements are mounted to a centralelectrically non-conductive mounting substantially perpendicular theupper electrode and passing through the centre of each conductiveelement within the first set of conductive elements of the one or moresets of conductive elements; and the set of conductive elements of theone or more sets of conductive elements having the outermost annularrings are mounted to a plurality of electrically non-conductive mountingelements disposed at predetermined positions around the periphery of theone or more sets of conductive elements.
 17. The antenna according toclaim 12, wherein a first set of conductive elements of the one or moresets of conductive elements are of a predetermined geometry; and anyother set of conductive elements of the one or more sets of conductiveelements is a series of annular implementations of the predeterminedgeometry; and the predetermined geometry exhibits symmetry for a 90°rotation.
 18. The antenna according to claim 12, further comprising aplurality of sets of electrically non-conductive connectors; wherein afirst set of conductive elements of the one or more sets of conductiveelements are of a predetermined geometry; any other set of conductiveelements of the one or more sets of conductive elements is a series ofannular implementations of the predetermined geometry; the predeterminedgeometry exhibits symmetry for a 90° rotation; each set of electricallynon-conductive connectors of the plurality of sets of electricallynon-conductive connectors couples an inner conductive plane of theplurality of conductive planes in a set of conductive elements to anouter conductive plane of the plurality of conductive planes in anotherset of conductive elements; and the set of conductive elements of theone or more sets of conductive elements having the outermost annularrings are mounted to a plurality of electrically non-conductive mountingelements disposed at predetermined positions around the periphery of theone or more sets of conductive elements.
 19. The antenna according toclaim 12, further comprising a plurality of sets of electricallynon-conductive connectors; wherein a first set of conductive elements ofthe one or more sets of conductive elements are of a predeterminedgeometry; any other set of conductive elements of the one or more setsof conductive elements is a series of annular implementations of thepredetermined geometry; the predetermined geometry exhibits symmetry fora 90° rotation; the one or more sets of conductive elements do notoverlap radially from a longitudinal axis along which the one or moresets of conductive elements are disposed; each set of electricallynon-conductive connectors of the plurality of sets of electricallynon-conductive connectors couples an inner conductive plane of theplurality of conductive planes in a set of conductive elements to anouter conductive plane of the plurality of conductive planes in anotherset of conductive elements; and the first set of conductive elements ofthe one or more sets of conductive elements are mounted to a centralelectrically non-conductive mounting substantially perpendicular theupper electrode and passing through the centre of each conductiveelement within the first set of conductive elements of the one or moresets of conductive elements.
 20. The antenna according to claim 12,further comprising a plurality of sets of electrically non-conductiveconnectors; wherein a first set of conductive elements of the one ormore sets of conductive elements are of a predetermined geometry; anyother set of conductive elements of the one or more sets of conductiveelements is a series of annular implementations of the predeterminedgeometry; the one or more sets of conductive elements do not overlapradially from a longitudinal axis along which the one or more sets ofconductive elements are disposed; the predetermined geometry exhibitssymmetry for a 90° rotation; each set of electrically non-conductiveconnectors of the plurality of sets of electrically non-conductiveconnectors couples an inner conductive plane of the plurality ofconductive planes in a set of conductive elements to an outer conductiveplane of the plurality of conductive planes in another set of conductiveelements; the first set of conductive elements of the one or more setsof conductive elements are mounted to a central electricallynon-conductive mounting substantially perpendicular the upper electrodeand passing through the centre of each conductive element within thefirst set of conductive elements of the one or more sets of conductiveelements; and the set of conductive elements of the one or more sets ofconductive elements having the outermost annular rings are mounted to aplurality of electrically non-conductive mounting elements disposed atpredetermined positions around the periphery of the one or more sets ofconductive elements.